The trend for more hot-and-spicy items on fast food menus has been marinating for a while, and is turning white hot just as we’re reaching the coldest time of the year.

Fast food menus must always feature the old reliable favorites. But in order to avoiding being seen as bland and boring, restaurant chains are constantly tweaking the options and giving customers fresh reasons to pop in and fill up. One of the most popular ways of spicing things up is regularly rolling out limited-time offers like McDonald’s St. Patrick’s Day-themed Shamrock Shake and this past summer’s big hit, Wendy’s Pretzel Bacon Cheeseburger.

Lately, a barrage of fast food outlets is spicing things up by literally spicing things up. Burger King and Wendy’s recently both added spicy sandwiches to their value menus (another hot fast food trend), with BK offering a couple of spicy-barbecue Rodeo sandwiches for $1 each and Wendy’s charging 99¢ for the Spicy Chipotle Crispy Chicken Sandwich or the Spicy Chipotle Jr. Cheeseburger. Sonic, meanwhile, added a Salsa Verde burrito to its breakfast menu, and Subway unveiled a new Jalapeno-Cheddar Bread on January 1, not long after it debuted a series ofSriracha sauce sandwiches nationally.

Sriracha has become the “it” ingredient among spicy menu items, according to Nation’s Restaurant News. The craze over Sriracha reached new heights a month ago, when fans of the hot sauce were in a panic because the supply of Sriracha was limited due to food safety regulations. “Sriracha” has become a buzzword on restaurant menus, as has “Chipotle,” which refers not only to a hot pepper used in Mexican cooking but of course to Chipotle, the fast-casual restaurant pioneer and one of the biggest quick-service eatery success stories seen in recent times. “Habanero” is yet another hot restaurant term, as in McDonald’s Bacon Habanero Ranch Quarter Pounder, introduced this past spring.

What is it with spiciness all of a sudden? The chains are basically responding to changing demographics and changing consumer tastes that call for spicier food. According to a report from Technomic, and food and beverage consulting firm, more than half of consumers (54%) said that hot or spicy foods are appealing, compared to 48% in 2011 and 46% in 2009. Younger diners ages 18 to 34 were most likely to crave spicy menu items, but polls indicate that spicier foods are hotter across nearly all age demographics. So be delivering the heat, fast food chains are simply offering what more diners want.